1. Field of the Invention
The present invention relates in general to illuminated indicator gauges used, for example, as speedometers and tachometers for a motor vehicle or the like, and more particularly to such gauges of a type which has a visual alarm indicator.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional gauge of the above-mentioned type will be described with reference to FIGS. 3 and 4 of the accompanying drawings.
As is seen from FIG. 3, the gauge comprises a meter panel 1 formed with circular openings 3a and 3b which have respective dial boards 2a and 2b received therein. The meter panel 1 has further two visual alarm indicators 4a and 4b mounted thereto and a turning direction indicator 5 mounted thereto.
FIG. 4 shows in detail the meter panel 1 and each of the visual alarm indicators 4a and 4b mounted to the meter panel 1.
The meter panel 1 comprises a transparent base plate 1a made of a rigid plastic, such as polycarbonate or the like, a transparent coloured layer 1b printed on a back surface of the base plate 1a and a smoked layer 1c printed on a front surface of the base plate 1a. The layer 1b is usually coloured red, blue or yellow. A fluorescent transparent substance layer 1d is coated on the smoked layer 1c except the portions with which the visual alarm indicators 4a and 4b and the turning direction indicator 5 are associated. As is known, the fluorescent substance layer 1d emits visible and visionary light under the action of ultraviolet rays. An electric ultraviolet lamp 10 is arranged in front of the meter panel 1.
Each visual alarm indicator 4a or 4b comprises various opaque marks le printed on the smoked layer 1c, lamp housings 6 each having an open end connected to the back surface of the meter panel 1 at the position where the corresponding mark 1e is located, and alarm electric lamps 7 respectively installed in the lamp housings 6.
Thus, when one of the alarm lamps 7 is energized to light upon sensing any trouble of the vehicle, the limited surrounding of the corresponding opaque mark 1e is illuminated to emphasize the mark 1e. With this, a viewer, that is, a driver, can recognize the vehicle trouble.
Of course, none of the alarm lamps 7 lights when the vehicle is in order.
However, due to its inherent construction, the conventional gauge has the following drawbacks.
That is, when, at night, the front surface (that is, the fluorescent substance layer 1d) of the meter panel 1 is visionally illuminated under the action of ultraviolet rays from the ultraviolet lamp 10, the portions of the meter panel 1 where the visual alarm indicators 4a and 4b are positioned appear dark. This phenomenon makes the external view of the illuminated meter panel 1 poor. Furthermore, the difference in brightness between the illuminated portion of the meter panel 1 and the non-illuminated portions of the same sometimes causes difficulties to arise in clearly and quickly reading the indicia on the dial boards 2a and 2b.